Why do we have different seasons? Why is that while certain places on the earth’s surface experience heat filled summers, others experience extremely cold winters at the same time? And what is the deciding factor that establishes which place would experience season at which time of the year? Here are some answers that might help us out.
In sharp contrast to the general notion that the different seasons we experience are caused by the earth’s orbit around the sun and that the individual seasons are governed by the distance between the earth and the sun during this period, it has been established that the seasons we experience are actually caused by the earth spinning on its own axis as it orbits the sun.
The earth’s axis is slightly tilted at an angle of 23 ½ degrees w.r.t. the orbital plane. This means that when the axis points at the sun during the earth’s rotation, the hemisphere near it experiences summer. When the axis moves away from the sun, that particular hemisphere experiences winter. This would most probably experience the summer) and winter solstices (‘solstice’ translates to ‘the sun stands’ in Latin) experienced at the North and South poles, and the other parts of the earth. While the summer solstice usually occurs somewhere around the third week of June every year, the winter solstice would occur somewhere around the third week of September every year.
The earth’s spin axis tilts at an angle of 90 degrees from the sun during these two periods (usually between March and September). This would explain spring and autumn equinox (translates to ‘equal night’ in Latin) wherein we experience equal hours of day and night (approx. 12 hours each).
Let’s take another basic example. Take a piece of blank paper and keep it on the floor. Shine a torchlight directly above it. The light from the torch would fall directly on the paper and would be concentrated in a single circle. Now tilt the paper sideways so that the light reflection on it takes the form of an eclipse, covering more area on the paper with lesser intensity. This is what typically happens to the earth as well.
When the earth’s axis is pointing directly at the sun, the sun’s rays would be concentrated on that particular hemisphere alone (which explains the heat experienced during summer) while leaving the opposite hemisphere uncovered (which explains the freezing winters). When the axis moves away from the sun, the rays need to spread over a larger area and so would be reduced in intensity (which explains the pleasant climate during spring and autumn).
